Question

A lorry starts from Bangalore to Mysore at 6 a.m , 7 a.m., 8 a.m. ......10 pm. Similarly one another starts from Mysore to Bangalore at 6 a.m , 7 a.m., 8 a.m. ......10 pm. A lorry takes 9 hours to travel from Bangalore to Mysore and vice versa.
(i) A lorry which has started at 6 am will cross how many lorries.
(ii) A lorry which had started at 6 pm will cross how many lorries .

Answer 1

a) A lorry beginning at $6$ am reaches its destination at :

$6.00+9$ hrs

$=15.00hrs=3P.M$

This time, the$10$ pm lorry arrives at $7$ a.m

Therefore the lorries it crosses along the way are :

The$7$ am lorry, the $8$ a. m lorry, the$6$ a. m lorry and the $10$ p.m

Total is :$4$ lorries.

b) the time differences are :

Between$6$pm and $6$am =$12$ hrs

$6$pm - $7$ am = $11$ hrs

$6$pm to $8$ am = $10$ hrs

$6$pm to $10$ pm =$4$ hrs

Since$4hrs<9$ hrs this lorry crosses the $10$ pm lorry.

Hence the answer is $1$ lorry.